Fluid Dynamic Design Optimization of the Intake of a Small Turbojet

This paper proposes an efficient gradient-based optimization procedure for black-box simulation codes and its application to the fluid-dynamic design optimization of the intake of a small-size turbojet, at high load and zero flight speed. Two simplified design criteria have been considered, which avoid to simulate the flow in any turbojet components other than the intake itself. Both design optimizations have been completed in a computational time corresponding to that required by eight flow analyses and have provided almost coincident optimal profiles for the intake. The flow fields computed with the original and the optimal profiles are compared to demonstrate the flow pattern improvements that can be theoretically achieved. Finally, the original and the optimal profiles have been mounted on the same small-size turbojet and experimentally tested, to assess the resulting improvements in terms of overall performances. All numerical and experimental results can be obviously extended to the intake of a microturbine for electricity generation.

Vapour Compression and Liquid Desiccant Hybrid System for Air Conditioning

The present study examines the performance of a hybrid air-conditioning system in which a vapour compression inverse cycle is integrated with an air dehumidification system working with hygroscopic solution and hydrophobic membrane. This approach may prove to be a valid alternative to the traditional summertime air-conditioning system, which involves cooling the air to below its dew point and subsequently reheating it. The system examined simultaneously cools and dehumidifies the air in an air-LiCl solution membrane vapour exchanger before it enters the conditioned environment. The LiCl solution is cooled by means of a vapour compression inverse cycle that uses the refrigerant KLEA 407C. The heat rejected by the condenser is used to regenerate the solution. A SIMULINK calculation programme was used to simulate the system in steady-state conditions. The performance of the system was analysed on varying significant operating parameters and was compared with that of a traditional direct-expansion air-conditioning plant. The results of the simulations revealed significant power saving which, in certain operating conditions, was as much as 50%.

Specific Performance Calculations of Two Types of Space Solar Power Systems

Space solar power systems (SSPSs) lately planned in Japan are introduced with a result of conceptual design studies. Solar energy collected in orbit is converted into electrical energy and is transmitted to the Earth by way of microwaves or lasers. Systems of our concern are thereby Microwave-based SSPS (MSSPS) and Laser-based SSPS (LSSPS). The MSSPS basically consists of solar concentrators and a disk-like power module with I- or Y-shaped radiator. The power module is one-sidedly coated with solar cells and is internally loaded with magnetrons. The LSSPS is composed of a sun-oriented parabolic mirror and a planar radiator put on the focal line, where an array of laser devices are set up. For any of the two, system feasibilities critically depend on possibilities of size/mass reduction and heat rejection. Radiative heat transfer/exchange analyses are made considering the system thermal balance. Analysis results are written in fractional form upon the specified transmission power P. The required area A and the resulted mass M are thus simply calculated from the specific area a and the specific mass m, respectively defined as A/P and M/P. All such performance indices concerning the concentrator/mirror, the generator, the radiator, and the system are expressed in algebraic form suited to numerical computations. Empirically obtained polynomial expressions are presented to determine the cell/magnetron/laser efficiencies from the specified temperature because the system size may be highly temperature-dependent. Performance calculations have been parametrically done with various combinations of the reference temperature and the concentration ratio. Obtained numerical results are graphically shown in the figures to indicate specific system/subsystem area/mass values. Such specific values are submitted to quantitative discussion in two demonstrative design cases. Design objects are then a low-earth orbiting MSSPS of 100 kW class and a geostationary-orbiting LSSPS of 1 MW class. System feasibilities of the two are mainly examined from thermal and configurational points of view.

Multi-Point Energy and Exergy Analysis of a 1.5 MWe Hybrid SOFC-GT Power Plant

This paper presents a multi-point energy and exergy analysis of a hybrid SOFC–GT power plant. The plant layout consists of the following principal components: an internal reforming SOFC, a steam-methane pre-reformer, a catalytic burner, a radial gas turbine, a centrifugal air compressor, a centrifugal fuel compressor, plate-fin heat exchangers, counter-flow shell and tube heat exchangers, and mixers. The partial load performance of the centrifugal compressors and radial turbine is determined using maps, properly scaled in order to match required mass flow rate and pressure ratio values. The plant is simulated on the basis of a zero-dimensional model discussed in previous papers. Two different partialization strategies are introduced in order to assess the partial load behavior of the plant. Results show that the plant achieves the best partial load performance for the case when both air and fuel mass flow rates are simultaneously reduced.

Phase Interaction in Hydroxylapatite/CaTiO3 Composite

Hydroxylapatite composites with calcium titanium oxide were prepared with pressureless air sintering for 2 hours at different temperatures between 500°C and 1300°C. The interaction between the phases was monitored with XRD analysis. At sintering temperatures near 1100°C, slight decomposition of hydroxylapatite and formation of tricalcium phosphate was observed. However, sintering at the temperature higher than 1100°C, tricalcium phosphate disappeared most probably due to the incorporation of CaTiO3 in the hydroxylapatite structure.

Fuzzy Statistics Approach for Aviation GTE Condition Estimation Technique

In this paper is shown that the probability-statistic methods application, especially at the early stage of the aviation gas turbine engine (GTE) technical condition diagnosing, when the flight information has property of the fuzzy, limitation and uncertainty is unfounded. Hence is considered the efficiency of application of new technology Soft Computing at these diagnosing stages with the using of the Fuzzy Logic and Neural Networks methods. Training with high accuracy of fuzzy multiple linear and non-linear models (fuzzy regression equations) which received on the statistical fuzzy data basis is made. Thus for GTE technical condition more adequate model making are analysed dynamics of skewness and kurtosis coefficients’ changes. Researches of skewness and kurtosis coefficients values’ changes show that, distributions of GTE work parameters have fuzzy character. Hence consideration of fuzzy skewness and kurtosis coefficients is expedient. Investigation of the basic characteristics changes’ dynamics of GTE work parameters allows to draw conclusion on necessity of the Fuzzy Statistical Analysis at preliminary identification of the engines’ technical condition. Researches of correlation coefficients values’ changes shows also on their fuzzy character. Therefore for models choice the application of the Fuzzy Correlation Analysis results is offered. For checking of models adequacy is considered the Fuzzy Multiple Correlation Coefficient of Fuzzy Multiple Regression. At the information sufficiency is offered to use recurrent algorithm of aviation GTE technical condition identification (Hard Computing technology is used) on measurements of input and output parameters of the multiple linear and nonlinear generalised models at presence of noise measured (the new recursive Least Squares Method (LSM)). The developed GTE condition monitoring system provides stage-by-stage estimation of engine technical conditions. As application of the given technique the estimation of the new operating aviation engine temperature condition was made.

Compact Basis Free Relations for Stress Tensors Conjugate to Hill’s Strain Measures

If the double contraction of a stress tensor such as T and rate of a Lagrangean strain tensor such as E, i.e. T : E˙, produces the stress power then these stress and strain tensors are called a conjugate pair. The applications of the conjugate stress and strain measures are in the development of the basic relations in nonlinear continuum mechanics analysis such as modeling of constitutive equations of elastic-plastic materials. In this paper relations for stress tensors conjugate to an arbitrary Lagrangean strain measure of Hill’s class are obtained. The results of this paper are more compact and simpler in compare with those available in the literature. The results are valid for the three dimensional Euclidean inner product space and the case of distinct eigenvalues of the right stretch tensor U.

Performance Evaluation of a Small Scale High Efficiency Cogeneration System

In recent years, a big effort has been made to improve microturbines thermal efficiency, in order to approach 40%. Two main options may be considered: i) a wide usage of advanced materials for hot ends components, like impeller and recuperator; ii) implementing more complicated thermodynamic cycle, like combined cycle. In the frame of the second option, the paper deals with the hypothesis of bottoming a low pressure ratio, recuperated gas cycle, typically realized in actual microturbines, with an Organic Rankine Cycle (ORC). The object is to evaluate the expected nominal performance parameters of the integrated-combined cycle cogeneration system, taking account of different options for working fluid, vapor pressure and component’s performance parameters. Both options of recuperated and not recuperated bottom cycles are discussed, in relation with ORC working fluid nature and possible stack temperature for microturbine exhaust gases. Finally, some preliminary consideration about the arrangement of the combined cycle unit, and the effects of possible future progress of gas cycle microturbines are presented.

Development of Membrane Contactors for Greenhouse Climate Control

Cultivation in greenhouse requires high water quantity for irrigation and sometimes for internal climate conditioning. Water resource is becoming more and more poor. The proposed system allows making greenhouses self-sufficient from the point of view of water needs and self-conditioned at a very low energy cost. Moreover it could allow cultivation in areas where drinkable water is scarce, since it can use as primary source saline or brackish water. This is a new concept of greenhouse, patented by Centro Ricerche FIAT (CRF), in which membranes, waterproof but permeable to vapor, are used in order to improve a cooling system. The management of membrane contactors allows, with lower energy expense with respect to standard air conditioning systems, allows to control both temperature and lowest humidity level inside the greenhouse, thus reducing water need. Saline water is used upstream for cooling and clean water is obtained, by means of downstream condensation.

A Novel Method on Singularity Analysis in Parallel Manipulators

A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a better understanding of geometrical interpretation of singularities in parallel mechanisms. Here we have introduced the Constraint Plane Method (CPM) and some of its applications in parallel mechanisms. The main technique used here, is based on Ceva Theorem.